As the power grid construction of China is improved increasingly, the extra high voltage transmission line becomes the backbone of the power grid frame of China, which also has a higher requirement on the maintenance work. Especially as the 660 kV grade of direct current transmission line is firstly applied in China, in order to ensure the normal operation of the transmission line and that troubles found during the operation of the transmission line can be solved timely, to thereby ensure the safe operation of the direct current transmission line, it is necessary to develop a set of tools for the maintenance of the transmission line in operation.
One of the primary contents of the maintenance work of the transmission line is to repair and replace an insulator. Most high voltage transmission lines are supported on a crossarm via an insulator which plays a fundamental role of supporting the wire and preventing the current from returning to the ground in the aerial transmission lines. The 660 kV grade of direct current transmission line, compared with the extra high voltage and ultrahigh voltage transmission lines in operation currently, employs a different material, for example, the wire is the aluminum conductor steel reinforced of 4×JL/G3A-1000/45 mm2, and the distance between the electrodes of the wire is 18 m. The linear insulator is a V-type composite insulator which has a length of 8.5 m in the light polluted area and 9.2 m in the heavy polluted area. And the tension insulator string is a 550 kN double porcelain insulators in parallel. Influenced by the length of the string of the insulators and the electric clearance, the tower head for carrying the insulators and the transmission lines has a large size, and affected by the project, the vertical load of the lines increases accordingly, which causes the change of the tension, the length and the like, thereby has a higher requirement on the replacement of the insulator in aspects such as the tension and the length. At present, maintenance tools for the transmission line at a voltage grade below 500 kV have been more perfect, however, due to the increase of the voltage grade, the diameter of the transmission line and the length of the insulator string are increased. Thus the maintenance tools have been far from the requirements for the replacement.